XRISM Reveals a Remnant Torus in the Low-luminosity AGN M81*
Bibliographic record
Abstract
Abstract Up to 40% of galaxies in the local Universe host a low-luminosity active galactic nucleus (LLAGN), making it vital to understand this mode of black hole accretion. However, the presence or absence of Seyfert-like geometries—an accretion disk close to the black hole, an optical broad-line region, and a molecular torus—remains uncertain owing to the low flux levels of sources within this class. Herein we present an analysis of an XRISM/Resolve spectrum of M81*, the LLAGN in the heart of the nearby spiral galaxy M81. A weak, neutral Fe K emission line is detected and resolved into K α,1 and K α,2 components. It shows a negligible velocity shift and weak broadening (FWHM = 46 0 − 160 + 260 km s − 1 ) that corresponds to an inner emission radius of r ≥ 2.7 × 104 GM c −2 for likely inclinations. The Fe Kα line likely traces a torus. The upper limit on additional splitting of the Fe Kα line components translates to a limit on the local magnetic field of B ≤ 3.5 × 108 G, assuming Zeeman splitting. The spectra also reveal ionized plasma(s) through He-like Fe xxv and H-like Fe xxvi emission lines. These can be fit equally well assuming photoionization and collisional excitation. The H-like Fe xxvi line is better described when a second component is included with a redshift of v = 1600 km s−1, but this addition is of marginal statistical significance. We discuss these results in the context of radiatively inefficient accretion flow models, magnetically arrested disks, and possible links to the Fermi bubbles in the Milky Way.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".